The present disclosure relates to a semiconductor structure, and particularly to a dynamic random access memory (DRAM) cell including a self-aligned laterally extended strap to connect an inner electrode of a trench capacitor and a finFET access transistor, and a method of manufacturing the same.
Trench capacitors are used in a variety of semiconductor chips for high areal capacitance and low device leakage. Typically, a trench capacitor provides a capacitance in the range from 4 fF (femto-Farad) to 120 fF. A trench capacitor may be employed as a charge storage unit in a dynamic random access memory (DRAM), which may be provided as a stand-alone semiconductor chip, or may be embedded in a system-on-chip (SoC) semiconductor chip.
A strap structure is employed to electrically connect an inner electrode of a trench capacitor to a source of an access field effect transistor. In the case of an access fin field effect transistor, the strap structure must extend through an insulator layer underlying the access fin field effect transistor to provide electrical connection between the inner electrode of trench capacitor and the source region of the access fin field effect transistor. Because other conductive structures such as passing gate lines are formed near the strap structure, formation of strap structure requires precise alignment of the source region and the inner electrode to avoid unintentional electrical shorts to other conductive structures. Thus, formation of strap structures tends to limit the scaling of a dynamic random access memory cell through overlay limitations with respect to various other conductive structures.